This invention relates to a biochemical method for determining the fertilization potential in sperm of oligospermic men and, in particular, to a method which utilizes the separation and measurement of particular enzymes in the cellular physiology of the spermatozoa.
The testicle serves as a site for spermatogenesis, sperm production and sperm maturation. Diagnosis of possible problems in spermatogenesis is normally carried out with the determination of sperm concentrations in the ejaculate. The sperm count fluctuates in all men, but due to the occasional lack of sperm, is more distinct in oligospermic (OS) patients with sperm counts below the 20.times.10.sup.6 sperm/ml normal level of normospermic (NS) patients. Low sperm concentrations may be due to pituitary problems, deficient hormone levels, testicular disorders, age, environmental factors, fever or excess heat, exposure to organic solvents in the work place, etc.
It has been found that the incidence of male factor or cause is about 40% in infertile couples. The overwhelming majority of these infertile and subfertile men are oligospermic and/or asthenospermic (sperm motility is lower than 40%). Management problems exist with respect to the oligospermic patients, as these men may try to father children for years because of the absence of methods to predict or establish the fertilizing potential, or lack of it. With intrauterine placement of the sperm or with in vitro fertilization, the pregnancy rates for couples with male factor infertility are only about 20%. This is in spite of the absence of the difference in sperm concentrations and motility among the fertile and infertile oligospermic husbands. It is increasingly apparent that the assessment of sperm quality in oligospermic specimens based on objective biochemical parameters is an essential need for the management of male infertility.
Beyond the classical semen analysis parameters, i.e., sperm concentration, motility and velocity, present approaches to evaluate selected sperm functions include the assessment of motile sperm yield following migration or "swim-up", the cervical mucus penetration test; measurements of acrosine activity, i.e., the enzyme which facilitates sperm penetration; the hypoosmotic sperm swelling procedure which probes the integrity of the sperm membrane; and analysis of sperm motion patterns. None of these tests address the overall physiological soundness of the spermatozoa or show high correlation with fertilizing potential. Even the human sperm zona-free hamster oocyte penetration test, which is a more related biological approach, is more consistent on the negative side (e.g. penetration rates below 15-20% and diminished success in human in vitro fertilization) than it is a measure of fertility.
Bearing in mind the problems in the prior art, it is therefore an object of the present invention to provide an objective biochemical measurement which can predict fertilization potential in oligospermic men.
It is another object of the present invention to provide a method for testing sperm which provides a relatively high degree of accuracy in predicting when fertilization is likely to occur.
It is a further object of the present invention to provide a test of sperm fertilization potential which utilizes a single ejaculate.
It is another object of the present invention to provide a method to determine the cellular maturity of spermatozoa.